Charged particles in crossed and longitudinal electromagnetic fields and beam guides

We consider a class of electromagnetic fields that contains crossed fields combined with longitudinal electric and magnetic fields. We study the motion of a classical particle (solutions of the Lorentz equations) in such fields. Then, we present an analysis that allows one to decide which fields from the class act as a beam guide for charged particles, and we find some time-independent and time-dependent configurations with beam guiding properties. We demonstrate that the Klein-Gordon and Dirac equations with all the fields from the class can be solved exactly. We study these solutions, which were not known before, and prove that they form complete and orthogonal sets of functions.Comment: 14 page

Selenium emission control at high temperatures with mineral sorbents, Final report, September 1, 1993--August 13, 1994

The focus of this project is on toxic heavy metal removal by sorbent injection in the upper-furnace region of a coal-fired boiler. Selenium is chosen as the candidate heavy metal to be studied because of its high volatility and associated difficulty in removal. The preliminary sorbent screening experiments were performed in a differential reactor, built in the first year of this project. A host of sorbents, such as, alumina, kaotinite, limestone and also hydrated lime were tested at a reaction temperature of 900{degrees}C, and for reaction duration of 4 hrs. The reason for choosing these minerals was because of their proven moderate to high capability of lead and cadmium capture, and also for moderate selenium capture at high temperatures, reported by recent studies. The sorbent screening experiments have used selenium dioxide as the Se source, since in the oxidizing atmosphere of the furnace, that is reported to be the existing form of selenium species. The preliminary sorbent screening experiments have shown that Ca(OH){sub 2} is the most promising sorbent for selenium capture out of all the sorbents tested. A careful review of the sorption results for Ca(OH){sub 2} has also revealed the strong possibility for occurrence of a chemical reaction. Since Se belongs to group VI of the periodic table along with sulfur, and shares many common properties with the latter, formation of a calcium selenite (CaSeO{sub 3}) or selenate (CaSeO{sub 4}) compound is likely by the reaction of CaO with SeO{sub 2}. The captured selenium has exhibited poor leachability in water, a property which is also shared by CaSeO{sub 4}. The presence of CaSeO{sub 4} is confirmed by the X-ray diffraction analysis of the sorbent sample. Preliminary studies for investigating the effect of temperature on SeO{sub 2}/Ca(OH){sub 2} reaction have shown that the percent of water-leachable selenium increases with decreasing reaction temperature

Bedforms of Thwaites Glacier, West Antarctica: Character and Origin

Bedforms of Thwaites Glacier, West Antarctica both record and affect ice flow, as shown by geophysical data and simple models. Thwaites Glacier flows across the tectonic fabric of the West Antarctic rift system with its bedrock highs and sedimentary basins. Swath radar and seismic surveys of the glacier bed have revealed soft-sediment flutes 100 m or more high extending 15 km or more across basins downglacier from bedrock highs. Flutes end at prominent hard-bedded moats on stoss sides of the next topographic highs. We use simple models to show that ice flow against topography increases pressure between ice and till upglacier along the bed over a distance that scales with the topography. In this basal zone of high pressure, ice-contact water would be excluded, thus increasing basal drag by increasing ice-till coupling and till flux, removing till to allow bedrock erosion that creates moats. Till carried across highlands would then be deposited in lee-side positions forming bedforms that prograde downglacier over time, and that remain soft on top through feedbacks that match till-deformational fluxes from well upglacier of the topography. The bedforms of the part of Thwaites surveyed here are prominent because ice flow has persisted over a long time on this geological setting, not because ice flow is anomalous. Bedform development likely has caused evolution of ice flow over time as till and lubricating water were redistributed, moats were eroded and bedforms grew

Practice-Based Learning and Professional Education

This chapter discusses some ways in which practice-based learning experiences can be used in sustainable ways within professional education. It proposes that learning through engagement in authentic practice-based experiences is increasingly seen as an essential component of initial occupational preparatory programs offered through universities. Yet, how those experiences are organised and enacted, and integrated with the other experiences that comprise students' curriculum will be central to the quality of the learning outcomes they secure. In particular, it is proposed that a scholarly teaching practice needs to be developed by those who organise and enact these experiences (i.e. university teachers) that effectively engages, supports and integrates the contributions arising from student engagement in practice settings. It is proposed that existing concepts and practices within educational science may not always be helpful in guiding the effective utilisation of these experiences in educational programs, because its base is limited and new challenges are emerging. Hence, academics need to develop their understandings and these practices, and thereby inform both their practice and that science. This case is made through considering the nature and contributions of learning through practice, how that relates to the provision of professional education and ways in which the utilisation of these experiences can be sustainable and effective. In doing so, it draws upon the findings of a recent national teaching fellowship program involving 20 projects across a range of disciplines within six Australian universities that comprised university teachers engaging in projects that addressed practice-based concerns.Arts, Education & Law Group, School of Education and Professional StudiesNo Full Tex

Analysis of semi-solid processing for metal matrix composite synthesis using factorial design

The main goal in this work is to conduct a quantitative analysis of the mechanical stir casting process for obtaining particulate metal matrix composites. A combined route of stirring at semi-solid state followed by stirring at liquid state is proposed. A fractional factorial design was developed to investigate the influence and interactions of factors as: time, rotation, initial fraction and particle size, on the incorporated fraction. The best incorporations were obtained with all factors at high levels, as well as that very long stirring periods have no strong influence being particle size and rotation the most important factors on the incorporated fraction. Particle wetting occurs during stirring at semisolid state, highlighting the importance of the interactions between particles and the alloy globularized phase. The role of the alloying element Mg as a wettability-promoting agent is discussed. The shear forces resulting from the stirring system is emphasized and understood as the effect of rotation itself added to the propeller blade geometry.São Paulo State Univ UNESP, Dept Mat & Technol, BR-12516410 Guaratingueta, SP, BrazilSão Paulo State Univ UNESP, Prod Dept, BR-12516410 Guaratingueta, SP, BrazilSão Paulo State Univ UNESP, Dept Mat & Technol, BR-12516410 Guaratingueta, SP, BrazilSão Paulo State Univ UNESP, Prod Dept, BR-12516410 Guaratingueta, SP, Brazi